K. De Mesel

An out-of-plane grating coupler for efficient butt-coupling between compact planar waveguides and single-mode fibers

We have designed and fabricated an out-of-plane coupler for butt-coupling from fiber to compact planar waveguides. The coupler is based on a short second-order grating or photonic crystal, etched in a waveguide with a low-index oxide cladding. The coupler is optimized using mode expansion-based simulations. Simulations using a 2-D model show that up to 74% coupling efficiency between single-mode fiber and a 240-nm-thick GaAs-AlO/sub x/ waveguide is possible. We have measured 19% coupling efficiency on test structures.

InP-based PIC for an optical phased-array antenna at 1.06 μm

We have demonstrated the feasibility of a photonic integrated circuit (PIC) for phase control at a wavelength of 1.06 /spl mu/m in an optical phased array telescope antenna system.

A new spot-size converter concept using fiber-matched antiresonant reflecting optical waveguides

We report on a new concept for InGaAsP-InP 1.55-/spl mu/m lasers with integrated spot-size converters (SSCs) based on antiresonant reflecting optical waveguides (ARROW). The mode expanders consist of a laterally tapered active region on top of a fiber-matched passive slab waveguide. The large slab mode is laterally confined by an antiresonant configuration of a couple of lateral waveguides defined in the same fabrication process as the active ridge. This feature makes the presented spot-size transformer as simple to fabricate as a standard waveguide, only requiring a planar growth step and a single conventional etch process. The fabricated tapers exhibit a low transformation loss and reduce the coupling loss to standard single-mode fibers from 8 to 4 dB. We also analyze by simulation two variants of the concept proposed in this work, including a taper structure for a buried waveguide, which are expected to show better performance. Simulation results show fiber-coupling efficiencies as low as 2.4 and 1.1 dB for both variants.

1.55-μm InP-InGaAsP Fabry-Perot lasers with integrated spot size converters using antiresonant reflecting optical waveguides

We demonstrate a new concept for InGaAsP-InP 1.55-/spl mu/m Fabry-Perot lasers integrated with spot size converters using type-A antiresonant reflecting optical waveguides. The fabrication of such devices allows to avoid the growth of thick layers of quaternary material with low Ga and As fraction, which are difficult to achieve and grow. Reduced far-field divergence angles (10/spl deg/ /spl times/ 27/spl deg/) and improved coupling to cleaved standard single-mode fibers (2.6-dB coupling loss) are achieved. The proposed device is compatible with conventional epitaxial techniques and lithographic methods.

Mode-expanded 1.55-/spl mu/m InP-InGaAsP Fabry-Perot lasers using ARROW waveguides for efficient fiber coupling

We report on a new concept for InGaAsP-InP 1.55-/spl mu/m lasers with integrated spot-size converters based on antiresonant reflecting optical waveguides (ARROWs). The mode expanders consist of a tapered active region on top of a fiber-matched passive vertical ARROW waveguide. The large fundamental leaky mode with its low propagation loss makes ARROW waveguides useful for fiber coupling functions and avoids typical growth-related problems as encountered with traditional designs. The tapers exhibit a low transformation loss and narrowed far-field emission patterns (10.4/spl deg//spl times/22/spl deg/) and reduce the coupling loss to standard single-mode fibers from 8 to 2.6 dB. We also present the design and the results obtained with a relaxed ARROW design with thinner ARROW layers to reduce the overall layer stack thickness considerably, without affecting the fiber-coupling performance. The antiresonant effect has also been used for the lateral confinement of the fiber-matched mode. This feature makes the presented spot-size transformer as simple to fabricate as a standard waveguide, only requiring a planar growth step and a single conventional etch process. The fabricated tapers exhibit a low transformation loss and minimum far-field divergence angles of 13.8/spl deg//spl times/30.8/spl deg/, reducing the coupling loss to a standard single-mode fiber from 8 to 4 dB. We also analyze by simulation two variants of the concept proposed in this work, including a taper structure for a buried waveguide, which are expected to show better performance. Simulation results show fiber-coupling efficiencies as low as 2.4 and 1.1 dB and reduced far-field divergence angles as low as 7.2/spl deg//spl times/14/spl deg/ and 7.2/spl deg//spl times/9/spl deg/ for both variants.

Integration of photonic functions in and with silicon

Silicon is gaining importance in photonic systems on a chip, either because of the importance of integrating photonic functions with electronic functions or because of the potential of silicon-based technology for photonics as such. In this paper, we discuss two distinct developments. The first is the development of nano-photonic integrated circuits based on photonic crystals or photonic wires. The second is the development of heterogeneously integrated active photonic components on top of silicon by means of wafer bonding.

Oxide-confined laser diodes with an integrated spot-size converter

We report a new technique for the monolithic integration of a GaAs-based InGaAs-GaAs strained quantum-well laser and a spot-size converter (SSC) to improve the fiber coupling characteristics. The selective wet oxidation of AlGaAs is used to simplify the fabrication scheme of the component to a single planar epitaxial growth step and one conventional noncritical etch. This approach also allows us to avoid the photolithography of narrow features. An excellent reproducibility of the fabrication scheme was found. The integrated SSC exhibits very low transformation losses and a low beam divergence of 7.5/spl deg//spl times/13.5/spl deg/. The coupling efficiency to a 980-nm single-mode fiber is improved from -6.34 dB for a reference laser to -1.49 dB for the tapered device. The -1-dB alignment tolerance is /spl plusmn/1.5 /spl mu/m in the transverse direction and /spl plusmn/1.6 /spl mu/m in the lateral direction, respectively.

InGaAsP-InP 1.55 /spl mu/m lasers with integrated mode expanders using fiber-matched leaky waveguides

We have successfully demonstrated a novel InGaAsP mode-expanded MQW laser based on the adiabatic transformation of the laser rib mode into a fiber-matched ARROW waveguide. The fabrication is drastically simplified to one planar growth step and one conventional non-critical etch step. Efficient mode transformation and considerable reduction of the horizontal and vertical far-field FWHM have been achieved.

InP-based PIC for an optical phased array antenna at 1.06 /spl mu/m

We have demonstrated the feasibility of a photonic integrated circuit for phase control at a wavelength of 1.06 /spl mu/m in an optical phased array telescope antenna system.